1. Field of the Disclosure
Embodiments of the present disclosure related generally to medical imaging, and more specifically to MRI imaging using a first nucleus scan constrained and regularized by a second nucleus scan.
2. Background of Related Art
Fluorine-19 (19F) has been used for in vivo imaging. Unfortunately, when used for magnetic resonance imaging (MRI), imaging using 19F is generally limited by low signal sensitivity and is often hindered by low signal-to-noise ratio (SNR) due, at least in part, to the limited number of 19F nuclei that can be delivered to an area of interest. In order to obtain reasonable voxel sizes during an in vivo imaging session, for example, dozens or hundreds of averaging scans are often used, resulting in lengthy scan times.
For cellular and molecular contrast agents, the concentration of agent that actually accumulates at the region of interest is limited by, for example, dose volume, particle size, receptor concentration, ligand concentration, and ligand specificity to the desired receptors. Fluorine is advantageous because it has no tissue background signal and thus, subtraction techniques are not required for signal detection. Unfortunately, the received signal still tends to be small due to the inherently low concentrations of agent delivered to the tissue. As a result, the signal often resides at or near the noise level in a typical experiment. For this reason, 19F MRI has been primarily used for cell tracking, either using pre-loaded cells, or through in situ labeling via macrophage phagocytosis of PFC-containing-particles in, for example, cancer, inflammation, infection, and ischemia models.
Conventionally, low SNR in 19F imaging has been addressed, for example, by (1) optimizing the relaxation properties of the fluorine-containing molecule, (2) delivering more chemically equivalent fluorine nuclei to the region of interest by optimizing the delivery mechanism (e.g., nanoparticle formulation or ligand affinities), or (3) optimization of acquisition techniques (e.g., pulse sequence) for a particular perfluorocarbon (PFC) particle construction.
Similar SNR issues arise in other instances, however, where small quantities of contrast agent are available. Thus, there is a clear need for acquisition and reconstruction methods to be developed to efficiently generate and utilize signal arising from small volumes of contrast agent. What is needed, therefore, are advanced reconstruction techniques for improving secondary-nucleus MRIs. The system and method can use multiple nucleus scans to regularize and reconstruct images to create improved images.
It is with respect to these and other considerations that the various embodiments described below are presented.